Please help me with the preposition "at".

I. What time is the movie? It's twenty-three to three.

II. When is the movie? It's at seven twenty tonight.


Why is "at" used in the second example but not in the first? What's the difference?

Thanks!!

The sentence is wrong.
What time does the actual movie start? At twenty-three to three.

What time is the movie? It starts at twenty-three to three.